How much is recorded power affected by wheel wheight

[R1000]

The Dynojet bench measures how fast the bike can increase the spinning rate of a drum and calculate the torque (and power). It is known that a light road tyre may read several hp more than a heavier track tyre. Chain friction of course also comes into the accuracy.

Has any of you dynoed with a real wide rim and tyre like e.g. 240 mm and can tell the hp reading difference vs. stock wheel?

 

[Professor]

I've got a dyno sheet at the house I'll try to find. Not exactly what you are looking for but it may give you an idea. We ran mine with a stock wheel then made a few passes with a Marvic and lighter tire. However the Marvic has ceramic bearings also.

 

[djsin]

i have no idea the numbers..but do no the lighter the weight the better the acceleration, and hp and torque should follow this rule as well

 

[Destin07]

The Dynojet bench measures how fast the bike can increase the spinning rate of a drum and calculate the torque (and power). It is known that a light road tyre may read several hp more than a heavier track tyre. Chain friction of course also comes into the accuracy.

Has any of you dynoed with a real wide rim and tyre like e.g. 240 mm and can tell the hp reading difference vs. stock wheel?

I've been wondering the same thing. I had a GEN 1 with a 240 that made 160HP on what I consider a VERY accurate dyno and it had a tune and akro full exhaust and PC. The 240 was made by RC component and it was god awful heavy

 

[dadofthree]

 

[BLUR]

I still have my stock wheels, but have been interested in the aftermarket ones. What I've read from different posts about them is that lighter wheels won't exactly give you a HP gain on the dyno, but due to the lighter weight, the engine will turn them easier, thus revs faster throught the gears. Now that would sound like it would equate to faster acceleration, which it does, but not that dramaticly. Some have said in the 1/4 it's only a tenth or two. Not much for a $2k+ investment. Lighter wheels seem to make a more signifigant difference tossing the bike around in the twisties than on the drag strip. At least this is what I have gathered from the here-say on the internet.:suspect:

 

[R1000]

A tenth or two on the quarter is huge, if this really is the typical difference between stock and wide wheels. It would be the same as perhaps a power difference of about 20 hp.

The questions remains though, have anyone dynoded the Busa with a stock and with a 240 wheel?

 

[GPW]

You need to do a negative HP test to see drag +/-

 

[R1000]

You need to do a negative HP test to see drag +/-

Can you elaborate ???

 

[GPW]

Your dyno operator should know how to do this. Its a feature on the 250i dyno. Some use it to test chains, oil, lighter wheels, drive train drag and so forth. Its called a negagtive HP test or Drag test for laymen terms.

 

[Mr Brown]

Weight reduction (particularly rotational mass) frees more power to accelerate the bike. In other words you do not gain power, but the power that was being used to turn the heavier wheels can now push your fat a$$ faster......

 

[Blanca BusaLess]

I dynoed my bike before with OEM wheels and 2500 miles on the OEM Bridgies then installed new Michelin HPXs along with a set of forged magnesium Marchesinis. Then we dynoed the bike again and it had gained almost 7hp. Now I cannot say for sure that I got all that from the wheels because I also changed the Muzzy 4into1 for a Brocks AH 4into1 but I would guess most of the 7hp gained came from the wheels because the bike was already dyno tuned with map and tweaked. I'm sure the Brocks added something over the Muzzy but I think most came from the lighter wheels. As far as seat of the pants feel and diffs the new wheels completely changed the bike all the way around !

 

[tclause]

Weight reduction (particularly rotational mass) frees more power to accelerate the bike. In other words you do not gain power, but the power that was being used to turn the heavier wheels can now push your fat a$$ faster......

 

[Mr Bogus]

Ryan had some numbers on this from his dyno and it was kind of substantial in some cases (5-10hp) just with tire changes..

Problem also is tire slippage.. the rear skins can get pretty toasty on the dyno (to the point of smoking)

Do a search here but you are correct, the rational mass of the tire will affect readings but that does not change the bhp, just the rwhp readings..

one of the downfalls of RWHP testing... is a bit subjective to tires, wheels that might not show up on the track.. BHP (crank shaft) is more accurate but has its pitfalls too.. Ideally? you could run both.. would give your your losses through the drive train..

no idea what negative hp test is however...

 

[Got-Busa?]

Ryan had some numbers on this from his dyno and it was kind of substantial in some cases (5-10hp) just with tire changes..

Problem also is tire slippage.. the rear skins can get pretty toasty on the dyno (to the point of smoking)

Do a search here but you are correct, the rational mass of the tire will affect readings but that does not change the bhp, just the rwhp readings..

one of the downfalls of RWHP testing... is a bit subjective to tires, wheels that might not show up on the track.. BHP (crank shaft) is more accurate but has its pitfalls too.. Ideally? you could run both.. would give your your losses through the drive train..

no idea what negative hp test is however...

This was one of many things that I pointed out in a certain pipe shoot out thread that used different bikes a while back. There is a big difference in tire changes on the dyno and other factors in the drive train.

I don't know the exact rate for rotation power calculations but you can figure a pound off a wheel is a little over 2lbs. off the bike. Dropping 5lbs. off a set of wheels is like dropping 10lbs. off the bike...

 

[Gymratt 64]

I was wondering what the over 200mph guys run. Lighter wheels or stock for the gyroscopic and flywheel effect..

 

[papi_ocho]

where the factories rate vehicles in stock form... set a baseline and go from there

by reducing "unsprung weight"
rims,tires,bolts,swingarms,brakes,shock! u are going to gain acceloration, and "agility" the bike is going to "feel" lighter. as far as HP goes.. does the bike increase HP by changing the fairings? NO!! will it cut thru the air better? YES!!
Posted via Mobile Device

 

[dragonbusa]

Weight reduction (particularly rotational mass) frees more power to accelerate the bike. In other words you do not gain power, but the power that was being used to turn the heavier wheels can now push your fat a$$ faster......

bingo! OH AND TWO TENTHS AT THE DRAG STRIP IS DIFFERANCE BETWEEN WINNING AND GETTING YOUR A$$ HANDED TO YA!

 

[GPW]

My personal opinion on wheel, tire, chain and sprocket based weight reduction is pretty easy. On throttle / off throttle response is enhanced when the drive train has less of a load or a task to achieve. i/e lets get the rear wheel moving. Some refer to this as the first moment of enertia when the wheel first starts to move.

Does this create horsepower as others have stated no, does it free it up, yes....for the wheel its like sprinting with a 10 pound back-pack, then sprinting without it. Using a very expensive 520 chain I was able to get my 2006 Busa with BST's to roll and feel like a 600 supper smooth, that bike is on its third owner now.

Everything just feels better less the weight. Some state for every (1) lb of weight loss achieved through rotational mass loss it is like or equal to (in theory) to 4 lbs of static weight removed from the vehicle. Having had almost every light weight wheel made it will always be on my list of the little stuff. Keep in mind if you get lighter wheels get the lightest rubber possible as well. Think of it as how fast can you run with 10lbs on your ankles vs. off, probably that same but off will just feel better.

 

[cwalker2]

I've see people lose 10 hp on by going to wide tire kits. I can't speak to what the wide kit was on a cruiser that we did but it was a 260 or larger. The poor guy lost 9 ponies over his previous set up.

Mr. Brown is right - so don't laugh. The engine's power doesn't change, but adding all that mass to the outside of such a huge fly wheel requires additional power to accelerate at the same rate. Therefore when using the same power the machine accelerates slower. In this case an additional 10 ponies was being used in inertia, drag and friction/stiction.

The way to see it is to do a step and hold test on the dyno. If you set it up to hold the engine still every 250 or 500 rpm and sample the power through the load cell you will get certain readings. Then do a sweep test and get those readings. Now install the wide tire kit. If you perform the step and hold guess what? similar readings to the original. You are not accelerating the added flywheel mass so it's out of the equation. The new sweep/inertia run will show the loss of power compared to the previous run however.

I've seen the big tire kits kill 2 or 3 horses at steady state testing by the way (So it's not Exactly the same). The extra drag from rubber on the drum and the extra jackshaft and chain eat power that will show up as drag. Therefore it shows up during step and hold/steady state testing.

I suppose you would see that in the negative power test although I hardly ever use negative power feature that my dyno has. I have my system configured to auto brake at the end of each sweep so I can quickly perform another run. Therefore I'm never letting her spin down for 10 minutes just to collect those types of numbers.